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3.
3SC161: Principlesof Information Technology
Data Communications is any transfer of data within a computer, between a computer
and another device, or between two computers.
Telecommunication is communications over a distance.
Tele- distance

4.
4SC161: Principlesof Information Technology
Data and Information travels through a communication system in the form of
eletromagnetic signals. Signals are represented in two ways
• Continuous waveform.
• Three basic components :
- Amplitude (Volt)
- Frequency (Hz)
- Phase (Radian)
• Infinite number of points between minimum and maximum amplitude.
• Use an Amplifier to increase power for transmission over long distances and
reduce noise by Filter.
• Used for Voice Communication.

5.
5SC161: Principlesof Information Technology
Data and Information travels through a communication system in the form of
eletromagnetic signals. Signals are represented in two ways
• Discrete waveform.
• Only two different values:
- 1 is high voltage/on electrical pulses.
- 0 is low voltage/off electrical pulses.
• The number of times a signal changes value per second is called “Baud rate”
• Use Repeater to transmission the data over long distances.
• Used for Data Communication.
time
amplitude(power)

8.
8SC161: Principlesof Information Technology
There are two principal line configurations.

9.
9SC161: Principlesof Information Technology
When two computers are in communication, data can flow in three ways:
A B
Only transmits. Only receives.
A B
Transmits when B receives. Transmits when A receives.
A B
Transmits and receives
while B transmits and received.
Transmits and receives
while A transmits and received.

20.
20SC161: Principlesof Information Technology
Fiber Optic Cable
A thin glass core surrounded by cladding that reflects light into the core, surrounded
by a protective plastic buffer/jacket.
• Light source is called a photo diode.
• Light travels through the core and bounces off of the cladding to "make turns"
• The signal degrades because of impurities in the glass
cladding
core

25.
25SC161: Principlesof Information Technology
Infrared Transmission • Using infrared-light waves at a frequency too low.
• Short-range communication (no more than 5 meters)
in IrDA standard.
• Cannot penetrate walls and work only in the direct
"line of sight"
• Speed less than 4 Mbps.
Radio Frequencies
• Distributes radio signals through the air.
• Speed more than 2 Mbps.
• Long distances: cellular phone, broadcast radio and TV.
• Short distances: Bluetooth and Wi-Fi

26.
26SC161: Principlesof Information Technology
Microwave • Transmits data more than 45 Mbps as High frequency radio wave.
• Sending signals from one microwave station to another.
• Line-of-sight transmission.

27.
27SC161: Principlesof Information Technology
Satellite • Microwave relay station in orbit around the earth.
• Transmitting a signal from a ground station is called “uplink”,
the reverse is called “downlink”

31.
31SC161: Principlesof Information Technology
Short-range wireless communication
The Bluetooth is a short-range wireless digital standard aimed at linking devices via
a piconet. The piconet typically has a range of about 10 m and a transfer rate between
about 400 and 700 kbps.

32.
32SC161: Principlesof Information Technology
Short-range wireless communication
The WiFi is a short-range wireless digital standard aimed at helping devices to
communicate with hi-speed at distances up to 10 m from access points. It is known
formally as an 802.11 Network.